The 100-month swift catalogue of supergiant fast X-ray transients

Abstract

The 100-month Swift Catalogue of Supergiant Fast X-ray Transients collects over a thousand Swift/BAT flares from 11 Supergiant Fast X-ray Transients (SFXTs), and reaches down to 15- 150 keV fluxes of about 6×10-10 erg cm-2 s-1 (daily timescale) and about 1.5×10-9 erg cm-2 s-1 (Swift orbital timescale, about 800 s). These hard X-ray flares typically last at least a few hundred seconds, reach fluxes in excess of 100mCrab (15-50 keV), and last much less than a day. Their clustering in the binary orbital phase-space, however, demonstrates that these short flares are part of much longer outbursts, lasting up to a few days, as previously observed in deeper Swift soft X-ray observations. We used this large dataset to probe the high and intermediate emission states in SFXTs, to infer the properties of these binaries, to estimate the number of flares per year each source is likely to produce as a function of the detection threshold and limiting flux. The catalogue was also recently used to estimate the expected number of SFXTs in the Milky Way.